submit: TxDescriptor<
    {
        update: {
            attested_header: {
                body_root: FixedSizeBinary<32>;
                parent_root: FixedSizeBinary<32>;
                proposer_index: bigint;
                slot: bigint;
                state_root: FixedSizeBinary<32>;
            };
            block_roots_branch: FixedSizeBinary<32>[];
            block_roots_root: FixedSizeBinary<32>;
            finality_branch: FixedSizeBinary<32>[];
            finalized_header: {
                body_root: FixedSizeBinary<32>;
                parent_root: FixedSizeBinary<32>;
                proposer_index: bigint;
                slot: bigint;
                state_root: FixedSizeBinary<32>;
            };
            next_sync_committee_update?: {
                next_sync_committee: {
                    aggregate_pubkey: FixedSizeBinary<48>;
                    pubkeys: FixedSizeArray<512, FixedSizeBinary<48>>;
                };
                next_sync_committee_branch: FixedSizeBinary<32>[];
            };
            signature_slot: bigint;
            sync_aggregate: {
                sync_committee_bits: FixedSizeBinary<64>;
                sync_committee_signature: FixedSizeBinary<96>;
            };
        };
    },
>

Submits a new finalized beacon header update. The update may contain the next sync committee.